Hydrothermal hydrolysis of halogenated compounds

ABSTRACT

A process for preparing a halogenated alcohol comprising hydrolyzing a halogenated precursor of the halogenated alcohol in water at a temperature near but below the critical point of water. For example, the halogenated alcohol has the formula CF 3 (CF 2 ) n CH 2 OH, wherein n is zero or a whole number from 1 to 5, the halogenated precursor has the formula CF 3 (CF 2 ) n CH 2 Cl, wherein n is as defined above, and the process comprises hydrolyzing the halogenated precursor in water at a temperature near but below the critical point of water. In a particularly preferred embodiment, the halogenated alcohol has the formula CF 3 CH 2 OH, the halogenated precursor has the formula CF 3 CH 2 Cl, and the process comprises hydrolyzing CF 3 CH 2 Cl in water at a temperature near but below the critical point of water.

This application claims benefit of provisional application 60/170,618filed Dec. 14, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to process for preparing halogenatedalcohols.

2. Description of Related Art

Currently most fluorinated alcohols and fluorinated organic acids aremanufactured in processes that depend heavily on large quantities ofhalogenated solvents. The proper handling and disposing of thesesolvents cause serious problems and costs for the industries that usethem.

SUMMARY OF THE INVENTION

The object of the present invention was to develop a process forpreparing halogenated alcohols that would not utilize halogenatedsolvents.

These and other objects were met by the present invention, which relatesto a process for preparing a halogenated alcohol comprising hydrolyzinga halogenated precursor of said halogenated alcohol in water at atemperature near but below the critical point of water.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference tothe drawings, wherein:

FIG. 1 is a graph showing the percentage of1,1,1-trifluoro-2-chloroethane [R133a] converted to trifluoroethanol[TFE] in a batch bomb reactor using the inventive process; and

FIG. 2 is a second graph showing the percentage of1,1,1-trifluoro-2-chloroethane [R133a] converted to trifluoroethanol[TFE] in a batch bomb reactor using the inventive process, but this timeafter 1 hour elapsed time.

DETAILED DESCRIPTION OF THE INVENTION

The inventive process provides a safer and less costly process forpreparing halogenated alcohols from the halogenated precursors thereof.The inventive process involves hydrolysis, i.e., the rupture of chemicalbonds by the addition of water. Accordingly, the phrase “halogenatedprecursor of said halogenated alcohol” is meant to embrace anyhalogenated compound that contains a functional group that can beconverted to a hydroxyl group upon reaction with water to thereby yielda halogenated alcohol.

In a preferred embodiment, the inventive process is used to makehalogenated alcohol compounds of the formula CF₃(CF₂)_(n)CH₂OH, whereinn is zero or a whole number from 1 to 5. In this embodiment, thehalogenated precursor has the formula CF₃(CF₂)_(n)CH₂Cl, wherein n is asdefined above, and the process comprises hydrolyzing said halogenatedprecursor in water at a temperature near but below the critical point ofwater.

In an especially preferred embodiment, the inventive process is used tomake trifluoroethanol [TFE], which has the formula CF₃CH₂OH. In thisembodiment, the halogenated precursor is 1,1,1-trifluoro-2-chloroethane[R133a], which has the formula CF₃CH₂Cl, and the process compriseshydrolyzing R133a in water at a temperature near but below the criticalpoint of water.

The critical point of water is 374° C. and 221 bar. The phrase “at atemperature near but below the critical point of water” means that thetemperature of the water during the reaction should be maintained nearbut below 374° C. By “near” is meant within 100° C. of the criticaltemperature. In the especially preferred embodiment, wherein R133a ishydrolyzed, the temperature is maintained from 275 to 325° C. atsubcritical pressure.

The time of the reaction is a result-effective-parameter, and personsskilled in the art will be able to optimize the yield of the halogenatedalcohol by varying the reaction time. In the especially preferredembodiment, wherein R133a is hydrolyzed to TFE, the reaction time ismaintained from 3 to 5 hours.

The invention will now be described in even greater detail withreference to the following example.

EXAMPLE

Exploratory hydrolysis of 1,1,1-trifluoro-2-chloroethane [R133a] totrifluoroethanol [TFE], (CF₃CH₂Cl+H₂O→CF₃CH₂OH+HCl) was performed insubcritical and supercritical water. The experimental reactor andprocedures used are discussed below.

Reactors. Batch bomb reactors were constructed of 316 stainless steeland had an outside diameter of 0.75 inch and an inside diameter of 0.51inch (wall thickness was 0.12 inch). Typical reactors were 7.5 incheslong providing an internal volume of 26.2 mL once fittings wereattached. The internal volume of each reactor was measured by fillingwith water. One end of the reactor was plugged. The other end had areducing union connected to 1/16 inch tubing (approximately 3 feet) thatwas attached to a valve. The valve allowed for the purging of theunpressurized system with nitrogen, feeding of gaseous reactants intothe reactor, and collection of the reactor contents. No directtemperature or pressure measurements were made on the reactor.

Once the reactor was sealed it was placed in an isothermal sand bath.The time required for heating the reactor (with only water in it) waspreviously measured with a thermocouple in place of the end plug forvarious sand bath temperatures. The heat up time was alwayssignificantly less (<5 min for the highest temperatures) than thereaction times (>30 mins). Therefore, the reaction temperature wasassumed to be the temperature of the sand bath.

The pressure of the system was calculated using the temperature, amountof water, volume of the reactor, and steam tables. Because the system isdilute in reactants, the pure water data used to calculate the pressureis sufficiently accurate.

To quench the reaction, the bomb reactor was removed from the sand bathand placed in an ice water bath. The reactor contents were thenanalyzed. Typical reaction times were from 30 minutes to 7 hours.

Feed and Collection Procedure. R133a has a normal boiling temperature of6.1° C. Therefore, it was stored as a saturated vapor-liquid mixture ina sealed lecture bottle without a regulator adapter at a pressure of 25psi (1.724 bar) and was delivered in the gas phase into the bombreactors.

The bomb reactors were disassembled and then washed with water and driedin the atmosphere at 150° C. for 4 hours. After cooling of the reactor,the bottom plug was placed on the reactor and a fixed amount of wateradded. The top 1/16 inch tubing and valve assembly was then attached.The system was purged with nitrogen for 10 minutes. A direct connectionto the lecture bottle was made to deliver gas to the bomb reactors. Thereactor was flushed twice with R133a before the final addition of thereactant. The amount of R133a added to the system was calculated fromthe available headspace in the reactor, the temperature, and pressureusing the ideal gas law, neglecting solubility of R133a in water.Similar drying and purging procedures were followed when a liquidreactant was used.

After cooling, the bomb reactors would return to their initial pressure(roughly atmospheric). The bomb reactors would be opened and the liquidanalyzed. To determine the unreacted R133a in the system the bombreactor was cooled to 0-3° C. and 8 ml of cold (−15° C.)tetrachloroethylene was injected into the reactor and shaken. Thereactor was sealed and placed in the freezer for 5-10 minutes. Thereactor was then opened and both the water and organic phases wereanalyzed for the starting material and desired product. The samples werekept close to 0° C. Only the water phase was analyzed for free Cl⁻ andF⁻. Control recovery experiments (i.e. reactors loaded with water andR133a without being heated) were performed and 90±5% of the R133a wasrecovered.

Analytical Techniques. Aqueous and organic samples were analyzed by GCFID. R133a, TFE, and trifluoroacetic acid were quantitatively measured.Aqueous samples were also analyzed for free chloride and free fluoride.Free chloride was measured by two methods, a chloride specific electrodeand a colorometric adsorption method (mercuric thiocyanate reacts withchloride ion to produce thiocyanate ion that is then reacted with ferricammonium sulfate to form red ferric thiocyanate that adsorbs at 463 nm).Free fluoride was measured with the SPADNS colorometric adsorptionmethod (fluoride ion reacts with a zirconium-dye lake, dissociating aportion of it to the colorless anion ZrF₆ ⁻² thus decreasing theadsorption at 570 nm).

Results. In the first set of experiments only the liquid phase wascollected and analyzed. Water fed into the reactor was in the range of 2to 8 mL (111 to 444 mmol) while R133a fed to the reactor was alwayssignificantly less (1.3 to 1.7 mmol) because it was delivered in the gasphase. The amount of water added to the system was chosen to preventtotal vaporization of the water at the desired reaction temperature thusnot allowing the pressure to exceed safety limits for this closed batchreactor. Reaction times were from 30 minutes to 7 hours. Temperaturesexplored were 240 to 425° C. Pressures were always calculated from thesaturation point of pure water given the volume of the reactor and thetemperature.

Table 1 contains the results for the hydrolysis of R133a in batchreactors when only the liquid phase was collected and analyzed. If R133areacts only through hydrolysis to TFE and HCl and the TFE does not reactfurther, then the amount of free chloride would be equal to the amountof TFE formed (on a mole basis). However, the measured Cl⁻ concentrationwas always higher. In addition, some fluoride was found showing thatsome other reactions are also occurring.

FIGS. 1 and 2 use the data presented in Table 1 to show how temperatureand reaction time affect the conversion of R133a to TFE. The conversionto byproducts is not accounted for in these figures.

TABLE 1 Hydrolysis of R133a, liquid phase analysis. Initial R133a toTemperature Pressure Time H₂O R133a TFE (° C.) (bar) (hr) (mmole)(mmole) (mole %) 240 34 3 444 1.27 0.09 240 34 7 444 1.27 0.16 275 60 1444 1.27 0.03 275 60 3 444 1.27 1.11 275 60 4 444 1.27 1.56 300 86 1 4441.27 0.07 300 86 2 444 1.27 2.20 300 86 3 444 1.27 11.21 300 86 3 4441.27 10.87 300 86 4 444 1.27 17.55 300 86 5 444 1.27 18.49 325 121 1 4441.27 0.20 350 165 1 222 1.54 0.20 400 185 1 111 1.68 0.01 425 227 1 1111.68 0.03 Note: The critical point of water is 374° C. and 221 bar. Tobe “supercritical,” both the temperature and pressure must be above thispoint. The last entry in Table 1 is supercritical, while the second tolast entry is only supercritical with respect to the temperature. Allother entries are subcritical.

Table 2 displays the results obtained from running batch bomb reactorexperiments in which R133a was recovered using the extraction into coldtetrachloroethylene method as described in the experimental section. Inall experiments 444 mmol of water and 1.27 mmol of R133a were charged tothe reactor. The percent of R133a recovered and converted to TFE isreported. The theoretical yield based on the R133a consumed is alsogiven.

Conclusions. Yields of TFE in the vicinity of 10% can be made at 275°C., but yields as high as 26% were made at 300° C. At 325° C. and highertemperatures, yields were lower even at shorter times of exposure. Theyields were quite low above the critical point of water.

No attempt was made to optimize the reaction conditions, but it isobvious that the hydrolysis of this type of halogenated compound, whileinert to water at the usual reaction conditions, can be effected byusing temperatures in the vicinity of the critical point of water, butnot exceeding it.

It will also be apparent to persons skilled in the art that theforegoing discovery is applicable to higher homologs of R133a and otherhalogenated compounds as well.

TABLE 2 Hydrolysis of R133a, liquid and extraction of vapor phaseanalysis. R133a to TFE R133a R133a TFE Temp Press. Time TFE MadeRecovered Consumed Yield (° C.) (bar) (hr) (mole %) (mmole) (%) (mmoles)(mole %) 275 60 1 0.03 0.00 10.18 1.14 0.03 275 60 3 1.12 0.01 11.091.13 1.26 275 60 3 1.02 0.01 89.42^(a) 0.13 9.64 300 86 2 2.20 0.03 9.981.14 2.44 300 86 2 2.80 0.04 69.47^(a) 0.39 9.17 300 86 2 4.49 0.0659.93^(a) 0.51 11.21 300 86 3 11.21 0.14 11.82 1.12 12.71 300 86 3 10.870.14 9.61 1.15 12.03 300 86 3 11.79 0.15 54.81^(a) 0.57 26.09 300 86 39.54 0.12 58.27^(a) 0.53 22.86 300 86 4 17.55 0.22 12.37 1.11 20.03 30086 4 15.52 0.20 31.66^(a) 0.87 22.71 300 86 5 17.55 0.22 9.6 1.15 19.41300 86 5 15.52 0.20 23.94 0.97 20.40 325 121 1 0.20 0.00 16.72 1.06 0.24325 121 2 1.02 0.01 40.97^(a) 0.75 1.73 325 121 3 1.10 0.01 6.83 1.181.18 ^(a)These entries used the cold tetrachloroethylene extractiontechnique. Note: For all of the conditions, 444 mmol of water and 1.27mmol of R133a were initially placed in the reactor.

It will further be appreciated that the instant specification and claimsare set forth by way of illustration and not limitations and thatvarious modifications and changes may be made without departing from thespirit and scope of the present invention.

1. A process for preparing a halogenated alcohol comprising hydrolyzinga halogenated precursor of said halogenated alcohol in water in theabsence of a carboxylic acid salt at a temperature near but below thecritical point of water.
 2. The process according to claim 1, whereinthe halogenated alcohol has the formula CF₃(CF₂)_(n)CH₂OH, wherein n iszero or a whole number from 1 to 5, the halogenated precursor has theformula CF₃(CF₂)_(n)CH₂Cl, wherein n is as defined above, and theprocess comprises hydrolyzing said halogenated precursor in water in theabsence of a carboxylic acid salt at a temperature near but below thecritical point of water.
 3. The process according to claim 2, whereinthe halogenated alcohol has the formula CF₃CH₂OH, the halogenatedprecursor has the formula CF₃CH₂Cl, and the process compriseshydrolyzing CF₃CH₂Cl in water in the absence of a carboxylic acid saltat a temperature near but below the critical point of water.
 4. Theprocess according to claim 1, which comprises hydrolyzing CF₃CH₂Cl inwater in the absence of a carboxylic acid salt at a temperature between275° C. to 325° C. at subcritical pressure.
 5. The process according toclaim 4, wherein said hydrolyzing is carried out for a period of 3-5hours.